Here's what to do if there's a tsunami

A tsunami warning was issued for parts of Alaska early Tuesday after a 7.9 magnitude earthquake rocked its southern coast, though it was later downgraded to an advisory. A watch was issued for the entire West Coast and Hawaii but it was canceled for California.

Water - one gallon of water per person per day for at least three days, for drinking and sanitationFood - at least a three-day supply of non-perishable foodBattery - powered or hand crank radio and a NOAA Weather Radio with tone alertFlashlightFirst aid kitExtra batteries

Whistle to signal for helpDust mask to help filter contaminated air and plastic sheeting and duct tape to shelter-in-placeMoist towelettes, garbage bags and plastic ties for personal sanitationWrench or pliers to turn off utilitiesManual can opener for foodLocal mapsCell phone with chargers and a backup battery

2. KNOW THE ALERT TERMS

As happened on Tuesday, the National Weather Service will use terms to keep you informed about potential tsunamis. What's the difference between a watch and a warning? Here's a look at each type of alert.

Warning A warning means that "a tsunami with the potential to generate widespread inundation is imminent or expected." Warnings may be cause for evacuations. As with all types of alerts, keep in mind that warnings can be updated, so you should always check tsunami.gov for the latest information.

Advisory An advisory means that significant inundation isn't expected, but there is still potential for strong waves and currents to pose danger to people near the water. An advisory may cause beaches to close or harbors to be evacuated.

Watch Watches are issued to alert those in a specific area that they should be prepared to take action if necessary. They may be upgraded or cancelled.

3. BE READY TO ACT

It's not enough to know what the terms mean. You should know what to do when you hear them.

Have a plan: Know your evacuation routes and shelters. Know how you will get in touch with your family and keep up-to-date on alerts. Know specific information your family might need, such as which evacuation centers accept pets, which medications your family members need and who is responsible for helping whom.

Make sure everyone in your family knows what to do by practicing your family plan.

4. GET SOMEWHERE SAFE HOWEVER YOU CAN

If you are asked to evacuate, you should do so immediately. Do not go to watch the tsunami and do not be fooled by receding water. It is not safe; it is "nature's tsunami warning."

If you are in an evacuation area but don't think you'll have time to get somewhere safe, ask emergency officials if there are nearby buildings that are tall or sturdy enough to provide protection.

5. STAY UNTIL IT'S SAFE

Once you get to a safe place, stay there until officials give the all-clear. A wave passing does not necessarily mean the danger is over, as a larger wave might be behind it.

6. CHECK FOR INJURIES

If you were in an affected area during the tsunami, check yourself and others for injuries before leaving the safe area. Contact emergency officials if needed.

7. BE CAREFUL RETURNING

After leaving the safe area, use caution. Do not go into a disaster area, as it could interfere with emergency response efforts. Be alert as you enter buildings, checking for damage. Don't go into a building that has water around it, as the floors may be damaged.